Download pages-articles.xml.bz2 from http://download.wikimedia.org/dewiki/20100206/
and extract the xml file using a compressor tool like 7zip.Wikiconvert tool
uncompress this file in the same folder as the xml and type:wikiconvert "your downloaded and extracted xml file" -owiki_prefix_like_enwiki -n
In some minutes you get some wiki_prefix_like_enwiki*.* files. Copy to the sdcard of your phone and run the wikipedia reader.
There is no problem having several wikipedias in your sdcard.